"My question remains, as I suspect that dry bone simulant would produce significantly different results from wet bone simulant..."

I just don't have the inclination to investigate the Swiss company in question, or the specifications of the product, but I would speculate that the product is a decent/excellent bone simulant, and probably accounts for moisture content, and as noted is comparably "brittle" as "real" bone. It does appear to plug bullets. Brass Fetcher provides a very detailed explanation of what they did and why they did it in terms of testing. As for Fackler not attempting to use any variations on ballistic gelatin testing, other than bare, the FBI and many others have recognized that adding clothing, drywall, sheet metal, glass, plywood, whatever, is real world. I appreciate all that Brass Fetcher has done and is doing in ballistic testing. Fackler's comment above on bullet/bone interaction is interesting, in that he calls it a "radical departure" from simple soft tissue, "when the bullet hits the bone" -

Fackler: "However, the only radical departure has been found to occur when the projectile strikes bone: this predictably deforms the bullet more than soft tissue..."

The testing I find most interesting is the Linebaugh Seminar, and the "Bone Box" where a large cow leg bone is placed in front of wet newspaper. And then some serious ammunition/bullets are tested for penetration. Very interesting results.